Module Objects
-
PyTypeObject
PyModule_Type
This instance of
PyTypeObject
represents the Python module type. This is exposed to Python programs astypes.ModuleType
.
-
int
PyModule_Check
(PyObject *p) Return true if p is a module object, or a subtype of a module object.
-
int
PyModule_CheckExact
(PyObject *p) Return true if p is a module object, but not a subtype of
PyModule_Type
.
-
PyObject*
PyModule_NewObject
(PyObject *name) Return a new module object with the
__name__
attribute set to name. The module’s__name__
,__doc__
,__package__
, and__loader__
attributes are filled in (all but__name__
are set toNone
); the caller is responsible for providing a__file__
attribute.New in version 3.3.
Changed in version 3.4:
__package__
and__loader__
are set toNone
.
-
PyObject*
PyModule_New
(const char *name) - Return value: New reference.
Similar to
PyImport_NewObject()
, but the name is a UTF-8 encoded string instead of a Unicode object.
-
PyObject*
PyModule_GetDict
(PyObject *module) - Return value: Borrowed reference.
Return the dictionary object that implements module‘s namespace; this object is the same as the
__dict__
attribute of the module object. This function never fails. It is recommended extensions use otherPyModule_*()
andPyObject_*()
functions rather than directly manipulate a module’s__dict__
.
-
PyObject*
PyModule_GetNameObject
(PyObject *module) Return module‘s
__name__
value. If the module does not provide one, or if it is not a string,SystemError
is raised and NULL is returned.New in version 3.3.
-
char*
PyModule_GetName
(PyObject *module) Similar to
PyModule_GetNameObject()
but return the name encoded to'utf-8'
.
-
void*
PyModule_GetState
(PyObject *module) Return the “state” of the module, that is, a pointer to the block of memory allocated at module creation time, or NULL. See
PyModuleDef.m_size
.
-
PyModuleDef*
PyModule_GetDef
(PyObject *module) Return a pointer to the
PyModuleDef
struct from which the module was created, or NULL if the module wasn’t created from a definition.
-
PyObject*
PyModule_GetFilenameObject
(PyObject *module) Return the name of the file from which module was loaded using module‘s
__file__
attribute. If this is not defined, or if it is not a unicode string, raiseSystemError
and return NULL; otherwise return a reference to a Unicode object.New in version 3.2.
-
char*
PyModule_GetFilename
(PyObject *module) Similar to
PyModule_GetFilenameObject()
but return the filename encoded to ‘utf-8’.Deprecated since version 3.2:
PyModule_GetFilename()
raisesUnicodeEncodeError
on unencodable filenames, usePyModule_GetFilenameObject()
instead.
Initializing C modules
Modules objects are usually created from extension modules (shared libraries
which export an initialization function), or compiled-in modules
(where the initialization function is added using PyImport_AppendInittab()
).
See Building C and C++ Extensions or Extending Embedded Python for details.
The initialization function can either pass a module definition instance
to PyModule_Create()
, and return the resulting module object,
or request “multi-phase initialization” by returning the definition struct itself.
-
PyModuleDef
The module definition struct, which holds all information needed to create a module object. There is usually only one statically initialized variable of this type for each module.
-
PyModuleDef_Base
m_base
Always initialize this member to
PyModuleDef_HEAD_INIT
.
-
char*
m_name
Name for the new module.
-
char*
m_doc
Docstring for the module; usually a docstring variable created with
PyDoc_STRVAR()
is used.
-
Py_ssize_t
m_size
Module state may be kept in a per-module memory area that can be retrieved with
PyModule_GetState()
, rather than in static globals. This makes modules safe for use in multiple sub-interpreters.This memory area is allocated based on m_size on module creation, and freed when the module object is deallocated, after the
m_free
function has been called, if present.Setting
m_size
to-1
means that the module does not support sub-interpreters, because it has global state.Setting it to a non-negative value means that the module can be re-initialized and specifies the additional amount of memory it requires for its state. Non-negative
m_size
is required for multi-phase initialization.See PEP 3121 for more details.
-
PyMethodDef*
m_methods
A pointer to a table of module-level functions, described by
PyMethodDef
values. Can be NULL if no functions are present.
-
PyModuleDef_Slot*
m_slots
An array of slot definitions for multi-phase initialization, terminated by a
{0, NULL}
entry. When using single-phase initialization, m_slots must be NULL.Changed in version 3.5: Prior to version 3.5, this member was always set to NULL, and was defined as:
-
inquiry
m_reload
-
inquiry
-
traverseproc
m_traverse
A traversal function to call during GC traversal of the module object, or NULL if not needed.
-
inquiry
m_clear
A clear function to call during GC clearing of the module object, or NULL if not needed.
-
freefunc
m_free
A function to call during deallocation of the module object, or NULL if not needed.
-
PyModuleDef_Base
Single-phase initialization
The module initialization function may create and return the module object directly. This is referred to as “single-phase initialization”, and uses one of the following two module creation functions:
-
PyObject*
PyModule_Create
(PyModuleDef *def) Create a new module object, given the definition in def. This behaves like
PyModule_Create2()
with module_api_version set toPYTHON_API_VERSION
.
-
PyObject*
PyModule_Create2
(PyModuleDef *def, int module_api_version) Create a new module object, given the definition in def, assuming the API version module_api_version. If that version does not match the version of the running interpreter, a
RuntimeWarning
is emitted.Note
Most uses of this function should be using
PyModule_Create()
instead; only use this if you are sure you need it.
Before it is returned from in the initialization function, the resulting module
object is typically populated using functions like PyModule_AddObject()
.
Multi-phase initialization
An alternate way to specify extensions is to request “multi-phase initialization”.
Extension modules created this way behave more like Python modules: the
initialization is split between the creation phase, when the module object
is created, and the execution phase, when it is populated.
The distinction is similar to the __new__()
and __init__()
methods
of classes.
Unlike modules created using single-phase initialization, these modules are not
singletons: if the sys.modules entry is removed and the module is re-imported,
a new module object is created, and the old module is subject to normal garbage
collection – as with Python modules.
By default, multiple modules created from the same definition should be
independent: changes to one should not affect the others.
This means that all state should be specific to the module object (using e.g.
using PyModule_GetState()
), or its contents (such as the module’s
__dict__
or individual classes created with PyType_FromSpec()
).
All modules created using multi-phase initialization are expected to support sub-interpreters. Making sure multiple modules are independent is typically enough to achieve this.
To request multi-phase initialization, the initialization function
(PyInit_modulename) returns a PyModuleDef
instance with non-empty
m_slots
. Before it is returned, the PyModuleDef
instance must be initialized with the following function:
-
PyObject*
PyModuleDef_Init
(PyModuleDef *def) Ensures a module definition is a properly initialized Python object that correctly reports its type and reference count.
Returns def cast to
PyObject*
, or NULL if an error occurred.New in version 3.5.
The m_slots member of the module definition must point to an array of
PyModuleDef_Slot
structures:
-
PyModuleDef_Slot
-
int
slot
A slot ID, chosen from the available values explained below.
-
void*
value
Value of the slot, whose meaning depends on the slot ID.
New in version 3.5.
-
int
The m_slots array must be terminated by a slot with id 0.
The available slot types are:
-
Py_mod_create
Specifies a function that is called to create the module object itself. The value pointer of this slot must point to a function of the signature:
-
PyObject*
create_module
(PyObject *spec, PyModuleDef *def)
The function receives a
ModuleSpec
instance, as defined in PEP 451, and the module definition. It should return a new module object, or set an error and return NULL.This function should be kept minimal. In particular, it should not call arbitrary Python code, as trying to import the same module again may result in an infinite loop.
Multiple
Py_mod_create
slots may not be specified in one module definition.If
Py_mod_create
is not specified, the import machinery will create a normal module object usingPyModule_New()
. The name is taken from spec, not the definition, to allow extension modules to dynamically adjust to their place in the module hierarchy and be imported under different names through symlinks, all while sharing a single module definition.There is no requirement for the returned object to be an instance of
PyModule_Type
. Any type can be used, as long as it supports setting and getting import-related attributes. However, onlyPyModule_Type
instances may be returned if thePyModuleDef
has non-NULLm_methods
,m_traverse
,m_clear
,m_free
; non-zerom_size
; or slots other thanPy_mod_create
.-
PyObject*
-
Py_mod_exec
Specifies a function that is called to execute the module. This is equivalent to executing the code of a Python module: typically, this function adds classes and constants to the module. The signature of the function is:
-
int
exec_module
(PyObject* module)
If multiple
Py_mod_exec
slots are specified, they are processed in the order they appear in the m_slots array.-
int
See PEP 489 for more details on multi-phase initialization.
Low-level module creation functions
The following functions are called under the hood when using multi-phase
initialization. They can be used directly, for example when creating module
objects dynamically. Note that both PyModule_FromDefAndSpec
and
PyModule_ExecDef
must be called to fully initialize a module.
-
PyObject *
PyModule_FromDefAndSpec
(PyModuleDef *def, PyObject *spec) Create a new module object, given the definition in module and the ModuleSpec spec. This behaves like
PyModule_FromDefAndSpec2()
with module_api_version set toPYTHON_API_VERSION
.New in version 3.5.
-
PyObject *
PyModule_FromDefAndSpec2
(PyModuleDef *def, PyObject *spec, int module_api_version) Create a new module object, given the definition in module and the ModuleSpec spec, assuming the API version module_api_version. If that version does not match the version of the running interpreter, a
RuntimeWarning
is emitted.Note
Most uses of this function should be using
PyModule_FromDefAndSpec()
instead; only use this if you are sure you need it.New in version 3.5.
-
int
PyModule_ExecDef
(PyObject *module, PyModuleDef *def) Process any execution slots (
Py_mod_exec
) given in def.New in version 3.5.
-
int
PyModule_SetDocString
(PyObject *module, const char *docstring) Set the docstring for module to docstring. This function is called automatically when creating a module from
PyModuleDef
, using eitherPyModule_Create
orPyModule_FromDefAndSpec
.New in version 3.5.
-
int
PyModule_AddFunctions
(PyObject *module, PyMethodDef *functions) Add the functions from the NULL terminated functions array to module. Refer to the
PyMethodDef
documentation for details on individual entries (due to the lack of a shared module namespace, module level “functions” implemented in C typically receive the module as their first parameter, making them similar to instance methods on Python classes). This function is called automatically when creating a module fromPyModuleDef
, using eitherPyModule_Create
orPyModule_FromDefAndSpec
.New in version 3.5.
Support functions
The module initialization function (if using single phase initialization) or a function called from a module execution slot (if using multi-phase initialization), can use the following functions to help initialize the module state:
-
int
PyModule_AddObject
(PyObject *module, const char *name, PyObject *value) Add an object to module as name. This is a convenience function which can be used from the module’s initialization function. This steals a reference to value. Return
-1
on error,0
on success.
-
int
PyModule_AddIntConstant
(PyObject *module, const char *name, long value) Add an integer constant to module as name. This convenience function can be used from the module’s initialization function. Return
-1
on error,0
on success.
-
int
PyModule_AddStringConstant
(PyObject *module, const char *name, const char *value) Add a string constant to module as name. This convenience function can be used from the module’s initialization function. The string value must be NULL-terminated. Return
-1
on error,0
on success.
-
int
PyModule_AddIntMacro
(PyObject *module, macro) Add an int constant to module. The name and the value are taken from macro. For example
PyModule_AddIntMacro(module, AF_INET)
adds the int constant AF_INET with the value of AF_INET to module. Return-1
on error,0
on success.
-
int
PyModule_AddStringMacro
(PyObject *module, macro) Add a string constant to module.
Module lookup
Single-phase initialization creates singleton modules that can be looked up in the context of the current interpreter. This allows the module object to be retrieved later with only a reference to the module definition.
These functions will not work on modules created using multi-phase initialization, since multiple such modules can be created from a single definition.
-
PyObject*
PyState_FindModule
(PyModuleDef *def) Returns the module object that was created from def for the current interpreter. This method requires that the module object has been attached to the interpreter state with
PyState_AddModule()
beforehand. In case the corresponding module object is not found or has not been attached to the interpreter state yet, it returns NULL.
-
int
PyState_AddModule
(PyObject *module, PyModuleDef *def) Attaches the module object passed to the function to the interpreter state. This allows the module object to be accessible via
PyState_FindModule()
.Only effective on modules created using single-phase initialization.
New in version 3.3.
-
int
PyState_RemoveModule
(PyModuleDef *def) Removes the module object created from def from the interpreter state.
New in version 3.3.